Cellular Ca2+ Dynamics in Urinary Bladder Smooth Muscle From Transgenic Mice Overexpressing Na+-Ca2+ Exchanger

The rise of Ca2+ concentration ([Ca2+] i ) by reducing external Na+ in urinary bladder smooth muscle cells (UBSMCs) from transgenic mice overexpressing Na+/Ca2+ exchanger type-1.3 (NCX1.3tg/tg) was about 4 times as large as that in the wild-type (WT). NCX1 protein expression in UB increased about 4-fold in NCX1.3tg/tg. The Ca2+ release by caffeine in UBSMCs was comparable between NCX1.3tg/tg and WT, but [Ca2+]i decay was faster in NCX1.3tg/tg. Contractions induced by acetylcholine, 60 mM K+, or electrical stimulation were significantly smaller in UB segments of NCX1.3tg/tg. NCX worked in Ca2+-extrusion mode during these contractions in UBSMCs of both WT and NCX1.3tg/tg. Keywords:: Na+-Ca2+ exchanger, urinary bladder smooth muscle, transgenic mouse